title: Molecular mechanism underlying phosphatidylinositol 4,5-bisphosphate-induced inhibition of SpIH channels.
abstract: Many ion channels have been shown to be regulated by the membrane signaling phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)). Here, we demonstrate that the binding of PIP(2) to SpIH, a sea urchin hyperpolarization-activated cyclic nucleotide-gated ion channel (HCN), has a dual effect: potentiation and inhibition. The potentiation is observed as a shift in the voltage dependence of activation to more depolarized voltages. The inhibition is observed as a reduction in the currents elicited by the partial agonist cGMP. These two effects were separable and arose from PIP(2) binding to two different regions. Deletion of the C-terminal region of SpIH removed PIP(2)-induced inhibition but not the PIP(2)-induced shift in voltage dependence. Mutating key positively charged amino acids in the C-terminal region adjacent to the membrane selectively disrupted PIP(2)-induced inhibition, suggesting a direct interaction between PIP(2) in the membrane and amino acids in the C-terminal region that stabilizes the closed state relative to the open state in HCN channels.
authors.affiliation: Department of Physiology and Biophysics, Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195-7290, USA.
authors.forename: Galen E
authors.initials: GE
authors.lastname: Flynn
authors.forename: William N
authors.initials: WN
authors.lastname: Zagotta
mesh_terms: D024342:Amino Acids, Acidic; D000818:Animals; D001665:Binding Sites; D006152:Cyclic GMP / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000819:agonists / Q000037:antagonists & inhibitors*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism / Q000494:pharmacology*; D015221:Potassium Channels / Q000819:agonists; D011485:Protein Binding; D012617:Sea Urchins
chemical_list: D024342:Amino Acids, Acidic; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D015221:Potassium Channels; D006152:Cyclic GMP